CN113657140A

CN113657140A - Phase detection of moving objects based on channel impulse response

Info

Publication number: CN113657140A
Application number: CN202110453131.5A
Authority: CN
Inventors: 斯特凡·泰尔蒂内克; 希尔瓦托·迭戈; 拉夫·洛德韦克·扬·罗弗斯
Original assignee: NXP BV
Current assignee: NXP BV
Priority date: 2020-05-12
Filing date: 2021-04-26
Publication date: 2021-11-16
Also published as: US20210359774A1; US11381329B2

Abstract

A moving object detector detects a moving object in a channel. The detecting comprises the detector receiving a plurality of frames based on the transmitter transmitting the plurality of frames over the channel. Determining one or more Channel Impulse Responses (CIRs) of the channel based on the received plurality of frames. The detector determines a CIR phase for each of the CIRs, and a phase signal is formed based on a phase value of the CIR phase for each of the CIRs. The detector compares the phase signal to a target signal and detects the moving object in the channel based on the comparison.

Description

Phase detection of moving objects based on channel impulse response

Technical Field

The present disclosure relates generally to moving object detection and, more particularly, to detecting moving objects based on the phase of a channel impulse response.

Background

Existing sensor technology measures the distance between a transceiver, such as a key fob carried by a person, and the vehicle so that the vehicle is unlocked when the person reaches the vicinity of the vehicle. This sensor technology also provides motion information using the doppler effect, enabling sensing of a kick (leg kick) at the rear bumper of the vehicle, which indicates that a person wants to open the trunk of the vehicle or detect vital signs of passengers in the vehicle, such as breathing rate and heart rate.

Disclosure of Invention

According to an aspect of the present invention, there is provided a method for detecting a moving object, the method comprising:

receiving, by a moving object detector, a plurality of frames transmitted through a channel;

determining, by the detector, one or more Channel Impulse Responses (CIRs) associated with the channel based on the received plurality of frames;

determining, by the detector, a CIR phase for each of the CIRs;

forming, by the detector, a phase signal based on a phase value of the CIR phase of each of the CIRs;

comparing, by the detector, the phase signal to a target signal; and

detecting, by the detector, the moving object in the channel based on the comparison.

In accordance with one or more embodiments, the phase values defining the CIR phases of each of the CIRs of the phase signals are located in a same time position in each of the CIR phases.

In accordance with one or more embodiments, the CIR phase and the phase signal define a phase value that varies according to time.

In accordance with one or more embodiments, forming the phase signal comprises: forming a first candidate phase signal and a second candidate phase signal, wherein the first candidate phase signal is associated with phase values located only at a first time position in each of the CIR phases and the second candidate phase signal is associated with phase values located only at a second time position in each of the CIR phases; and selecting the first candidate phase signal or the second candidate phase signal as the phase signal based on a respective amplitude or power associated with the first candidate phase signal or the second candidate phase signal exceeding a threshold level.

In accordance with one or more embodiments, the target signal defines a phase value that varies as a function of time, the phase value being indicative of a kick toward a vehicle, and wherein detecting the moving object comprises detecting the kick toward the vehicle.

According to one or more embodiments, the target signal defines a phase value that varies according to time, the phase value being indicative of a vital sign of a human being, and wherein detecting the moving subject comprises detecting the vital sign of the human being.

According to one or more embodiments, the target signal comprises a time-varying phase value, which characterizes the moving object.

In accordance with one or more embodiments, detecting the moving object in the channel includes determining that a correlation between the target signal and the phase signal exceeds a threshold level.

In accordance with one or more embodiments, detecting the moving object in the channel comprises providing a velocity of the moving object based on an amplitude of the phase signal.

In accordance with one or more embodiments, determining, by the detector, the one or more CIRs includes correlating one or more pulses of a pulse sequence of the received frame with an expected one or more pulses, the method additionally including transmitting a plurality of frames over the channel, wherein an Institute of Electrical and Electronics Engineers (IEEE)802.15.4 standard defines a format and content of the plurality of transmitted frames.

According to a second aspect of the present invention, there is provided a moving object detector comprising:

an analog/digital front end implemented with a circuitry to receive a plurality of frames from a channel;

a CIR estimator implemented with a circuitry system to determine one or more CIRs for the channel based on the received plurality of frames;

a phase extractor implemented with circuitry to determine a CIR phase for each of the CIRs and form a phase signal based on a phase value of the CIR phase for each of the CIRs; and

an object detector implemented with circuitry to compare the phase signal to a target signal and detect the moving object in the channel based on the comparison.

In accordance with one or more embodiments, the CIR phase and the phase signal have time-varying phase values.

According to one or more embodiments, the phase extractor for forming the phase signal comprises: circuitry for forming a first candidate phase signal and a second candidate phase signal, wherein the first candidate phase signal is associated with phase values located only at a first temporal location in each of the CIR phases and the second candidate phase signal is associated with phase values located only at a second temporal location in each of the CIR phases; and circuitry for selecting the first candidate phase signal or the second candidate phase signal as the phase signal based on a respective amplitude or power associated with the first candidate phase signal or the second candidate phase signal exceeding a threshold level.

According to one or more embodiments, the target signal defines a time-varying phase value associated with a kick towards a vehicle, and wherein the object detector for detecting the moving object comprises circuitry for detecting the kick towards the vehicle.

According to one or more embodiments, the target signal defines time-varying phase values, which are associated with vital signs of a human being, and wherein the subject detector for detecting the moving subject comprises circuitry for detecting the vital signs of the human being.

According to one or more embodiments, the object detector for detecting the moving object in the channel comprises circuitry for determining that a correlation between the target signal and the phase signal exceeds a threshold level.

In accordance with one or more embodiments, the object detector for detecting the moving object in the channel includes circuitry for providing a velocity of the moving object based on the phase signal.

In accordance with one or more embodiments, the detector additionally includes a transmitter implemented with the circuitry to transmit the plurality of frames over the channel, wherein an Institute of Electrical and Electronics Engineers (IEEE)802.15.4 standard defines a format and content of the plurality of transmitted frames.

Drawings

Fig. 1 is an example block diagram of a moving object detector for detecting a moving object.

Fig. 2 shows in more detail how the phase signal is generated by a moving object detector.

Fig. 3A-3C show example phase signals determined as a result of a person making multiple acceleration kicks to a moving object detector mounted on the rear bumper of a vehicle.

Fig. 4A-B illustrate detection of a vital sign, such as a heart rate or a breathing rate of a person, based on an example phase signal.

FIG. 5 is an example flow diagram of functionality associated with detecting moving objects by a moving object detector.

FIG. 6 is a block diagram of an example apparatus for detecting moving objects.

The drawings are for purposes of illustrating example embodiments, and it is to be understood that the embodiments are not limited to the arrangements and instrumentality shown in the drawings.

Detailed Description

The following description includes example systems, methods, techniques, and program flows for mobile object detection, and more particularly, detecting a mobile object based on a Channel Impulse Response (CIR) of a channel and, in particular, based on a time-domain representation of the CIR phase of the CIR. In an example, the CIR is determined by transmitting a Radio Frequency (RF) pulse and receiving the RF pulse based on the transmitted RF pulse reflected from the moving object. A phase signal of a phase value that varies according to time is determined based on a time-domain representation of the CIR phase of the CIR. The phase signal is then compared with a target signal to detect a moving object. Since the CIR is not converted to the frequency domain, e.g., the Fast Fourier Transform (FFT) of the CIR, the detection is performed in the time domain with low power consumption and low memory requirements. Well-known instructions, protocols, structures, and techniques have not been shown in detail in order not to obscure the description.

Example System

Fig. 1 is an example block diagram of a moving object detector 100 for detecting a moving object. Moving object detector 100 may include one or more components such as a transmitter 102, an analog/digital front end 104, a channel impulse response detector 122, a CIR estimator 124, a CIR pre-processor 126, a phase processing system 128, a phase extractor 130, and an object detector 132. Transmitter 102 may be implemented using circuitry, e.g., analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, and/or processing circuitry, that executes code stored in memory that, when executed by the processing circuitry, performs the disclosed functions of transmitter 102. Analog/digital front end 104 may be implemented using circuitry, e.g., analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, and/or processing circuitry, that executes code stored in memory that, when executed by the processing circuitry, performs the disclosed functions of analog/digital front end 104. Channel impulse response detector 122 may be implemented using circuitry, e.g., analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, and/or processing circuitry, that executes code stored in memory that, when executed by the processing circuitry, performs the disclosed functions of channel impulse response detector 122. The CIR estimator 124 may be implemented using circuitry, e.g., analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, and/or processing circuitry, that executes code stored in memory that, when executed by the processing circuitry, performs the disclosed functions of the CIR estimator 124. The CIR pre-processor 126 may be implemented using circuitry, such as analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, and/or processing circuitry, that executes code stored in memory that, when executed by the processing circuitry, performs the disclosed functions of the CIR pre-processor 126. Phase processing system 128 may be implemented using circuitry, e.g., analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, and/or processing circuitry that executes code stored in memory that, when executed by processing circuitry, performs the disclosed functions of phase processing system 128. Phase extractor 130 may be implemented using circuitry, e.g., analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, and/or processing circuitry that executes code stored in memory that, when executed by the processing circuitry, performs the disclosed functions of phase extractor 130. The object detector 132 may be implemented using circuitry, e.g., analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, and/or processing circuitry, that executes code stored in memory that, when executed by the processing circuitry, performs the disclosed functions of the object detector 132. In some embodiments, some of the components may be implemented with the same circuitry, e.g., the same processing circuitry executing different sets of code. The components may also be implemented in other ways.

In an example, moving object detector 100 may detect moving objects 106 in channel 108 based on processing of a Channel Impulse Response (CIR) from a received transmission in channel 108. The CIR represents the channel response of the channel resulting from the transmission of the pulse sequence 112 by the transmit antenna 142 of the transmitter 102 and the reception of the pulse sequence 154 by the receive antenna 120 of the analog/digital front end 104 over the channel 108 based on the transmitted pulse sequence 112. Channel 108 may be a transmission medium such as air for transmitted and received pulses. Further, the channel 108 may have one or more objects, such as a moving object 106 and a static object 118. The object may be a physical structure, and in some examples, the object may be part of a larger object. In one example, a person or a limb of a person may be an object, and when the person gestures with his limb, the object is a moving object, and when the limb is stationary, the object is a static object. In another example, a car may be an object, which is a moving object when the car is moving, and which is a static object when the vehicle is stationary. The moving object 106 and the static object 118 may affect the CIR due to the transmitted pulse sequence 112 reflecting off one or more objects in the channel 108, such as the moving object 106 and any static objects 118. For example, the amplitude of one or more pulses of the transmitted pulse train 112 may vary due to reflections on the moving object 106 and the static object 118, causing the pulse train 154 received by the receive antenna 120 to vary. As another example, the phase associated with the transmitted pulse sequence 112 may change due to reflections and doppler effects on the moving object 106, causing the pulse sequence 154 received by the receive antenna 120 to change.

Transmitter 102 may transmit one or more pulses 112 over channel 108 via transmit antenna 142. In an example, each pulse can be an increasing followed by decreasing amplitude of the electromagnetic wave, or a decreasing followed by increasing amplitude of the electromagnetic wave, and the sequence of pulses is a burst of such electromagnetic wave. The transmitter 102 may transmit two sequences 112 as shown, but may transmit more or fewer sequences, with each sequence being the same or different. The transmitted pulse sequence 112 may be arranged as a frame 114 of pulses, and in an example, the transmitter 102 may transmit a plurality of frames 114 separated by time intervals 116, where each frame 114 includes a respective pulse sequence 112. In some examples, the time interval 116 between frames 114 may be fixed, e.g., the time interval 116 between frames 114 is 1 millisecond, or the time interval 116 between frames 114 may vary. Further, in some examples, the Institute of Electrical and Electronics Engineers (IEEE)802.15.4 standard may specify an example format for frame 114. The frame 114 may have the format of one or more fields, such as a preamble and a data payload. The preamble may include one or more symbols, where each symbol may be the same and defined by one or more ternary codes. In an example, the preamble of frame 114 may have up to 512 symbols, and pulse sequence 112 may represent one or more symbols in the preamble of frame 114.

In an example, the transmitter 102 may be arranged to transmit a sequence of one or more pulses 112 by modulation on a carrier wave to form Radio Frequency (RF) pulses. The RF pulses may be synthesized from two amplitude modulated sinusoidal carriers, referred to as phase offsets of the in-phase and quadrature components, or from an in-phase amplitude modulated sinusoidal carrier. In some examples, the pulses may have a bandwidth of 500MHz and are transmitted at a carrier frequency in a range of 3.1GHz to 10.6GHz associated with an ultra-wideband (UWB) radar system.

The receive antenna 120 and the analog/digital front end 104 may receive the pulse train 154. The pulse sequence 154 is exemplary in nature and the sequence may depend on the characteristics of the moving object 106 and the static object 118. Further, in the example, a pulse sequence, such as pulse sequence 154, may define a frame. For example, the receive antenna 120 may be arranged as a chip receive antenna on a Printed Circuit Board (PCB). In some examples, analog/digital front end 104 may be a component of a real receiver to demodulate pulse sequence 154 when pulse sequence 112 is in-phase modulated on a carrier wave. In some examples, analog/digital front end 104 may be a component of a complex receiver to demodulate pulse sequence 154 when pulse sequence 112 is modulated in-phase (I) and quadrature (Q) on a carrier. Analog/digital front end 104 may include one or more signal processing components, such as low noise amplifiers, mixers, local oscillators, filters, and analog-to-digital converters, to facilitate this demodulation.

Analog/digital front end 104 may provide the received pulse sequence to channel impulse response detector 122. In an example, the received pulse sequence may be defined by a digital signal of data samples. The channel impulse response detector 122 may determine the CIR of the channel 108 based on a CIR estimator 124 and a CIR pre-processor 126. The CIR estimator 124 may determine the CIR. The inputs to the CIR estimator may be the received pulse sequence and the expected pulse sequence. In an example, the expected pulse sequence may indicate a transmitted pulse sequence 112, e.g., a symbol in a preamble of a frame 114 transmitted by the transmitter 102. During configuration of the channel impulse response detector 122, the expected pulse sequence may be stored in a memory (not shown) associated with the CIR estimator 128 and updated if the transmitted pulse sequence 112 changes. The CIR estimator 124 may perform cross-correlation between the received pulse sequence and the expected pulse sequence to estimate the CIR. In some examples, the cross-correlation may be a function of a displacement of the received pulse sequence relative to an expected pulse sequence, and a similarity measure of one pulse sequence relative to another pulse sequence.

The estimated CIR may be defined by a complex number having a real part and an imaginary part in a cartesian coordinate system. In an example, the estimated CIR may then be input into a CIR preprocessor 126 that preprocesses the CIR. The preprocessing by the CIR preprocessor 126 may include applying one or more filters, such as a moving average filter or a low pass filter, to the CIR. The moving average filter operates by averaging a plurality of points from the input signal to produce each point in the output signal. The point from the input signal may be the real component of the CIR and the output signal may have reduced high frequency noise. Alternatively, the point from the input signal may be an imaginary component of the CIR and the output signal may have reduced high frequency noise. The low pass filter may be a frequency response applied to the CIR that reduces high frequency noise of the CIR. Similarly, a low pass filter may be applied to the real or imaginary component of the CIR. The CIR processed by the CIR preprocessor 126 may be output to a phase processing system 128.

The phase processing system 128 may be arranged with a phase signal extractor 130 and an object detector 132. The phase processing system 128 may receive the CIR from the CIR detector 122 and detect the moving object 106 between the transmitter 102 and the analog/digital front end 104. The phase extractor 130 may determine the phase value of the CIR phase as a function of time by converting one or more complex numbers of the CIR to corresponding phase values associated with the polar coordinate system. The magnitude of the phase values may indicate the velocity of the moving object, with higher magnitudes indicating higher velocities and lower magnitudes indicating lower velocities. In an example, the phase extractor 130 may perform the conversion by a coordinate rotation digital computer (CORDIC) that converts the complex number of CIRs from a cartesian coordinate system to a polar coordinate system. The phase extractor 130 may store the CIR phase of the CIR in the memory 134 of the phase processing system 128 as CIR phase 1 … N. In the present example, the memory 134 shows three CIR phases 1, CIR phase 2, and CIR phase 3 stored in the memory 134, but a greater or lesser number of CIR phases may be stored. The phase extractor 130 may determine the phase signal 140 based on phase values associated with one or more of the CIR phases stored in the memory 134. The phase signal 140 may be a time-varying signal that characterizes how the phase values of the CIR phases of the respective CIRs vary over time. In some examples, phase signal 140 may be processed by a filter, such as a low pass filter, to reduce noise associated with the phase signal. The low pass filter may have the same frequency response as the low pass filter used by the CIR preprocessor 126 or a different frequency response.

The phase signal 140 may be provided to an object detector 132 that determines whether the phase signal 140 indicates the presence or absence of a moving object in the channel 108. The object detector 132 may have a comparator 136 to compare the phase signal 140 with a target signal 138. Target signal 138 may be a time varying signal of phase values resulting from movement of a particular object in channel 108. In an example, the target signal 138 may be stored in a memory (not shown) of the phase processing system 128 during configuration of the phase processing system 128 and/or updated based on the particular moving object to be detected. The object detector 132 may access this target signal and provide it to the comparator 136. The comparator 136 may compare the target signal 138 with the phase signal 140. Based on a comparison of the phase signal 140 with the target signal 138, which in the example defines a corresponding set of data points, a determination is made whether a particular moving object is detected. If the phase signal 140 and the target signal 138 are "similar" as described in further detail below, it is determined that a moving object is detected. If the comparison of the phase signal 140 to the target signal 138 is not "similar" as described in further detail below, it is determined that no moving object is detected. The object detector 132 may output an indication of this detection.

In an example, the phase signal comprises a time-varying phase value and the target signal comprises a time-varying phase value, which are compared to detect the moving object. In this regard, the phase signal and the target signal are in the time domain. Further, the phase signal is determined based on the CIR not converted into a frequency domain such as a Fast Fourier Transform (FFT). Since no frequency domain conversion is performed to detect moving objects, detection requires low power consumption and low memory requirements. Detecting moving objects by converting the CIR to the frequency domain (e.g., from a complex number of frequency variations) and analyzing it to detect moving objects increases power and/or memory requirements.

In an example, the moving object detector 100 may be a subsystem of a larger system. In one application, the moving object detector 100 may be located on the vehicle 144 to sense a moving object relative to the vehicle 144. For example, the moving object detector 100 may be positioned on a rear bumper 146 of the vehicle 144 to facilitate sensing of kicks under the rear bumper 146. A kick may indicate that a person wants to open the trunk of vehicle 144 and that the moving object to be detected is a leg. Additionally, or alternatively, the moving subject detector 100 may be located in the interior 148 of the vehicle 144 to facilitate detecting vital signs of the occupant in the vehicle 144, such as his breathing rate and heart rate. In another application, the moving object detector 100 may be located on a computing device, such as an internet of things (IOT) device 152, such as the illustrated lights or security devices, to facilitate detecting motion that turns on the lights or activates an alarm, respectively.

In an example, one or more of transmitter 102, analog/digital front end 104, channel impulse response detector 122, and phase processing system 128 may be implemented on the same Integrated Circuit (IC) or separate respective ICs. If the components are implemented on the same IC (e.g., to form a transceiver), transmitter 102 and analog/digital front end 104 may also be synchronized in phase to facilitate transmission and reception of pulse sequence 112. Synchronization may be provided by a local oscillator shared by the transmitter 102 and the analog/digital front end 104 on the IC. Transmitter 102 and analog/digital front end 104 may also be synchronized in phase to facilitate transmission and reception of pulse sequence 112 if transmitter 102 and analog/digital front end 104 are on separate respective ICs. In this example, transmitter 102 and analog/digital front end 104 may share an oscillator or have separate oscillators that are further synchronized. Furthermore, in some examples, one or more of the circuitry associated with transmitter 102, analog/digital front end 104, channel impulse response detector 122, and phase processing system 128 may be separated by a network, such as a Local Interconnect Network (LIN) or a Controller Area Network (CAN). For example, the CIR output by the CIR estimator 124 circuitry may be transmitted over a network to an Electronic Control Unit (ECU) having circuitry associated with the channel impulse response detector 122 and the phase processing system 128 to detect the moving object 106.

In an example, transmitter 102 and analog/digital front end 104 may also share a common antenna instead of transmitting and receiving pulse sequence 112 using respective antennas, shown as transmit antenna 142 and receive antenna 120. Transmitter 102 and analog/digital front end 104 may be coupled to this shared antenna and may time multiplex transmission and reception through this shared antenna. Further, in some examples, one of the

antennas

120 or 142 may include two or more antennas.

Fig. 2 shows in more detail how the phase signal is generated in the moving object detector 100. Transmitter 102 may transmit a plurality of frames 114 that cause analog/digital front end 104 to receive a plurality of frames 252-256 (which are similar to pulse sequence 154) via receive antenna 120 based on the transmitted plurality of frames 114. Each of the plurality of frames 252- > 256 may be associated with a respective pulse sequence, such as one of the pulse sequences 202- > 206. Further, in some examples, each frame may be separated by a fixed time interval 208, which may be 1 millisecond. In other examples, the time interval 208 may be variable.

The CIR estimator 124 knows that the transmitted pulse sequence 112 may be an expected pulse sequence. The CIR estimator 124 may correlate the expected pulse sequence with the received pulse sequence from frames 252-256 of the antenna 120 to determine the corresponding CIR of the channel 108 between the transmitter 102 and the receive antenna 120. For example, the CIR estimator 124 may correlate the received pulse sequence 202 with an expected pulse sequence to determine the CIR. In some examples, received pulse sequence 202 may include one or more repeated pulse subsequences, each of which may correspond to the same symbol. The repeated subsequences may be averaged together to remove noise and the averaged subsequences may be correlated with an expected pulse sequence to determine the CIR associated with the frame. In this example, the CIR may be determined for frame 252 having pulse sequence 202, may be determined for frame 254 having pulse sequence 204, and may be determined for frame 256 having pulse sequence 206.

The CIR may be represented by a plurality of complex numbers, and the phase extractor 130 may determine a phase value for each complex number, which may be in the range of-180 degrees to 180 degrees, or in some other range in the example. The aggregation of the phase values defines the CIR phase. Example CIR phases are shown as CIR phase 246, CIR phase 248, and CIR phase 250 corresponding to frame 252, frame 254, and frame 256, respectively. This process may be repeated as additional frames are received including the corresponding pulse sequence.

Each complex number forming a CIR phase may have a time index. The time index may define a time position in the CIR. The phase value associated with the complex number may have an associated time index. The time index may define a time position in the CIR phase. In this regard, the CIR phase 246 may be a plot of the phase value 210 (i.e., the magnitude of the phase) with a time index that varies with time along the time axis. In the example, the time index may also be referred to as a tap number (tap number), which uniquely identifies each phase value of the phase values 210. For example, the first phase value may be labeled tap 1, the second phase value may be labeled tap 2, the third phase value may be labeled tap 3, etc., where N is 3 tap values. The same number of taps for the phase values in the multiple CIR phases 246-250 indicates that the complex numbers used to generate the phase values have the same time index in the corresponding CIRs. For example, tap 2 in CIR phases 246, 248, and 250 may correspond to a complex number in the corresponding CIR with time index 2.

In an example, the phase value may be selected with the same number of taps across multiple CIR phases. To illustrate, tap 1 associated with each of the CIR phases 246 & 250 may be selected as shown by the phase values 224 & 228. The phase values 216 and 220 may be aggregated to form a candidate phase signal 230. In some examples, phase extractor 130 may interpolate phase values to define candidate phase signals 230. This process may be repeated for tap 2 selected for each CIR phase, as shown by

phase values

216 and 220. The phase values 216 and 220 may be aggregated to form a candidate phase signal 222. This process may continue for other taps, e.g., tap 3 selected for each CIR phase, tap 4 selected for each CIR phase, etc. Then, the phase extractor 130 may select one of the candidate phase signals as a phase signal output and then compare the phase signal with the target signal to detect the moving object. In some examples, the selection may be based on the magnitude of one or more of the candidate phase signals. For example, the selected phase signal may be one of the candidate phase signals that has the highest amplitude compared to the other candidate phase signals. As another example, the selected phase signal may be one of the candidate phase signals having the maximum power. As yet another example, the selected phase signal may have a maximum amplitude or power that exceeds a threshold level. The selection may also be based on other criteria in addition to or instead of amplitude and/or power.

The comparison of the phase signal to the target signal may include a value indicative of a correlation between the phase signal and the target signal. The comparison may involve calculating a normalized absolute error between the phase signal and the target signal. The phase signal matches the target signal if the normalized absolute error is less than a threshold amount. If the normalized absolute error is not less than the threshold amount, the phase signal does not match the target signal. The comparison of the phase signal to the target signal may alternatively comprise applying a matched filter associated with the target signal to the phase signal process. Matched filtering is a process for detecting a known signal (i.e., a target signal) embedded in noise. The matched filter applied to the phase signal may indicate the degree of matching between the target signal and the phase signal. If the degree of match exceeds a threshold amount, a moving object is detected. If the degree of match does not exceed the threshold amount, no moving object is detected. The comparison between the phase signal and the target signal may also be performed in other ways.

In an example, moving object detector 100 may take the form of a UWB radar sensor operating in the 6.5GHz band. Further, in some examples, the moving object detector 100 may be mounted on a rear bumper 146 of the vehicle 144. In this example, transmitter 102 transmits a plurality of pulse sequences. The analog/digital front end 104 may receive a plurality of pulse sequences based on the transmitted plurality of pulse sequences, and the moving object detector 100 may determine whether to open the trunk. For example, the object detector 132 may compare a phase signal determined based on the transmitted plurality of pulse sequences and the received plurality of pulse sequences with a target signal indicative of a kick. If the object detector 132 determines a match between the phase signal and the target signal, the trunk is opened. If the object detector 132 does not determine a match between the phase signal and the target signal, the trunk is not opened.

Fig. 3A-3C show example phase signals determined as a result of a person making multiple acceleration kicks to a moving object detector 100 mounted on a rear bumper of a vehicle. The example phase signal may be compared to a target signal to determine whether a kick is detected.

Fig. 3A shows a plurality of example phase signals 300 determined by detector 100, which result from an acceleration kick toward the rear bumper of the vehicle. Phase signal 300 is plotted as a function of phase value along axis 302 and time along axis 304. The CIR may be determined for each received pulse sequence associated with the respective transmitted pulse sequence. The phase signal may be determined using a phase value, e.g., tap N in each CIR phase of each CIR. For example, tap 17 as shown by CIR 17 may define a phase signal associated with each of the kicks shown as kicks 1-6, as well as phase signal 306 for kick 4. The phase signals of

taps

6, 8, 14 and 16 identified by CIR 6, CIR 8, CIR 14 and CIR 16 are also shown. Each kicked phase signal has a peak shape, and the magnitude of the phase of the peak increases with the time and speed of the kicking.

Fig. 3B shows an example of an enlarged view of phase signal 308 for one of the kicks. Phase signal 308 is plotted as a function of phase value along axis 302 and time along axis 304. The phase signal 308 has a phase slope that increases as the leg associated with the kick moves toward the moving object detector 100 and a phase slope that decreases as the leg moves away from the moving object detector 100. The increased phase slope is due to an increased doppler shift, which causes the phase shift of the carrier frequency of the received pulse to increase and indicate a higher velocity. Similarly, the phase slope decrease is due to a decrease in the doppler shift of the carrier frequency of the received pulse, which causes the phase shift to decrease and indicate a lower velocity. In this example, the phase signal 310 associated with CIR 17 may have a maximum phase shown by a phase value of 48 degrees and selected by the phase extractor 130.

Fig. 3C shows an example comparison between target signal 312 indicating a kick and phase signal 314 output by phase extractor 130. In the present example, target signal 312 may define a phase value that indicates kicks as a function of time. Target signal 312 and phase signal 314 are plotted as a function of phase values along axis 302 and time along axis 304. With the object detector 132, the phase signal 314 may be compared to the target signal 312 to determine whether a moving object associated with the target signal is detected. If the indication of the comparison exceeds a threshold amount, a moving object associated with the target signal is detected. If the indication of the comparison does not exceed the threshold amount, no moving object associated with the target signal is detected.

Fig. 4A-B illustrate the detection of a vital sign, such as a heart rate or a breathing rate of a person, based on the phase signal output by the phase extractor 130. The human may be in a vehicle, the transmitter 102 in the vehicle may transmit a plurality of frames, each frame having a pulse sequence, and the analog/digital front end 104 in the vehicle may receive a plurality of frames, each frame having a pulse sequence based on the transmitted frames. A human may sit quietly and breathe normally according to the example pattern 5x normal- >5x fast- > breath-hold- >5 x. Phase extractor 130 may determine a phase signal based on the transmitted frame and the received frame.

Fig. 4A shows a phase signal 400 associated with taps of CIR phases of multiple CIRs. The phase signal 400 indicates a moving object in the vehicle. In this example, the periodic phase peaks 1-5 correspond to moving objects in the form of breathing or breathing patterns of passengers in the vehicle.

Fig. 4B illustrates the scaling (zoom) of the phase signal 400 during the "breath hold" portion 402 of fig. 4A. The peaks 1-7 during the "breath hold" portion 402 indicate moving objects in the form of heart beats, which beat at approximately 7 times every 4 seconds or 105 bpm.

In this regard, the detector 100 has a resolution to detect vital signs such as respiratory rate and even heart rate of passengers in the vehicle without having to perform an FFT by matching the phase signal 400 with a target signal of two phase values that vary according to time. Moving object detection is performed with low power consumption and low memory requirements compared to in the frequency domain.

Example operations

Fig. 5 is an example flow diagram of functionality 500 associated with detecting moving objects by the detector 100. In an example, functions in function 500 may be implemented using circuitry, e.g., analog circuitry, mixed signal circuitry, memory circuitry, logic circuitry, and/or processing circuitry, that executes code stored in memory that, when executed by the processing circuitry, performs the disclosed functions.

At 502, transmitter 102 transmits a plurality of frames. Each frame comprises a sequence of pulses modulated on a carrier wave having a carrier frequency. Transmitter 102 transmits the pulse sequence over channel 108.

At 504, the analog/digital front end 104 receives a plurality of frames based on the transmitted plurality of frames. Each received frame may include a pulse sequence received based on a corresponding transmitted pulse sequence. In an example, the transmitted pulse sequence may be received directly by the receive antenna 120, as a received pulse sequence, or as a result of reflections in the channel 108 in the path between the transmitter 102 and the receive antenna 120 on the static object 118 and/or the moving object 106.

At 506, a CIR is determined for each received pulse sequence. The CIR estimator 124 may determine the CIR. The CIR may be based on a correlation between the received pulse sequence and a corresponding expected pulse sequence. In some examples, the CIR preprocessor 126 may use a filter, such as a low pass filter or a running average filter, to preprocess the CIR to remove noise in the CIR.

At 508, phase values for taps of the CIR phase associated with the CIR are determined to define a phase signal. The phase signal may be determined by phase extractor 130. In some examples, phase extractor 130 may determine a plurality of candidate phase signals, each associated with a different tap of the CIR phase associated with the CIR, and the phase signal having the greatest amplitude or maximum power may be the phase signal output by phase extractor 130. The phase value of the phase signal may be indicative of the speed at which the moving object moves over time. In some examples, the phase signal may additionally be pre-processed by a filter, such as a low pass filter, to remove noise in the phase signal.

At 510, the phase signal is compared to a target signal. As an example, the target signal may refer to a predetermined signal that illustrates a type of motion, such as kicking, breathing rate or heart rate. The comparison performed by the object detector 132 may indicate a correlation between the phase signal and the target signal. In an example, the comparison may be based on a matched filter or a normalized absolute error calculation.

If the comparison indicates that the degree of correlation exceeds a threshold amount, then at 512, a moving object associated with the target signal is detected. For example, the comparison may indicate that kicks were detected, that a heart rate was detected, or that a breathing pattern was detected. If the comparison indicates that the degree of correlation does not exceed the threshold amount, then at 514, no moving object associated with the target signal is detected.

At 516, the characteristics of the phase signal are output. The characteristic may be an amplitude of the phase signal indicative of a velocity of the moving object, or a frequency of a peak in a plurality of phase signals indicative of a breathing frequency or a heart rate of the person. The characteristics may be used to perform additional actions. For example, if a kick at a certain speed is detected, the trunk of the vehicle may be opened. As another example, if a breathing rate or heart rate is detected and the vehicle is locked, the doors may be unlocked to allow the passenger to exit the vehicle. Other variations are also possible.

FIG. 6 is an example block diagram of a computer device 600, such as the moving object detector 100, that performs functions associated with determining moving objects. Computer device 600 may have processing circuitry 602 (which may include multiple processors, multiple cores, multiple nodes, and/or implement multithreading, etc.) and memory 604, such as system memory (e.g., one or more of cache, SRAM, DRAM, zero-capacitance RAM, twin-transistor RAM, eDRAM, EDO RAM, DDR RAM, EEPROM, NRAM, RRAM, SONOS, PRAM, etc.), or any one or more other possible implementations of one or more non-transitory machine-readable media. The memory 604 may store computer code, program instructions, computer instructions, program code for performing one or more operations or control operations associated with the channel impulse response detector 122 or the phase processing system 128 via respective software modules 610 and 612. The computer device 600 also includes a bus 616 (e.g., PCI, ISA, PCI-Express) that couples the processing circuitry 602, the memory 604, and the interface 606. In some examples, interface 606 may include transmitter 102 and analog/digital front end 104 that receives pulses to be transmitted from bus 616 and sends pulses to be transmitted over bus 616.

In one embodiment, a method for detecting a moving object is disclosed. The method comprises the following steps: receiving, by a moving object detector, a plurality of frames transmitted through a channel; determining, by a detector, one or more Channel Impulse Responses (CIRs) associated with a channel based on the received plurality of frames; determining, by a detector, a CIR phase for each of the CIRs; forming, by a detector, a phase signal based on the phase value of the CIR phase of each of the CIRs; comparing, by a detector, the phase signal with a target signal; and detecting, by the detector, the moving object in the channel based on the comparison. In an embodiment, the phase values defining the CIR phase of each of the CIRs of the phase signals are located in the same time position in each of the CIR phases. In an embodiment, the CIR phase and phase signals define phase values that vary according to time. In an embodiment, a method of forming a phase signal includes: forming a first candidate phase signal and a second candidate phase signal, wherein the first candidate phase signal is associated with phase values located only at a first temporal position in each of the CIR phases and the second candidate phase signal is associated with phase values located only at a second temporal position in each of the CIR phases; and selecting the first candidate phase signal or the second candidate phase signal as the phase signal based on a respective amplitude or power associated with the first candidate phase signal or the second candidate phase signal exceeding a threshold level. In an embodiment, the target signal defines a phase value that varies as a function of time, the phase value being indicative of a kick toward the vehicle, and wherein detecting the moving object comprises detecting the kick toward the vehicle. In an embodiment, the target signal defines a phase value varying according to time, the phase value being indicative of a vital sign of a human being, and wherein detecting the moving object comprises detecting the vital sign of the human being. In an embodiment, the target signal comprises a phase value that varies according to time, said phase value characterizing the moving object. In an embodiment, a method of detecting a moving object in a channel includes determining that a correlation between a target signal and a phase signal exceeds a threshold level. In an embodiment, a method of detecting a moving object in a channel includes providing a velocity of the moving object based on an amplitude of a phase signal. In an embodiment, a method of determining one or more CIRs by a detector includes correlating one or more pulses of a pulse sequence of a received frame with an expected one or more pulses, the method additionally including transmitting a plurality of frames over a channel, wherein an Institute of Electrical and Electronics Engineers (IEEE)802.15.4 standard defines a format and content of the plurality of transmitted frames.

In another embodiment, a moving object detector is disclosed. The moving object detector includes: an analog/digital front end implemented with a circuitry to receive a plurality of frames from a channel; a CIR estimator implemented with a circuitry system to determine one or more CIRs of a channel based on a received plurality of frames; a phase extractor implemented with a circuitry system to determine a CIR phase for each CIR and form a phase signal based on a phase value of the CIR phase for each of the CIRs; and an object detector implemented with circuitry to compare the phase signal to a target signal and detect a moving object in the channel based on the comparison. In an embodiment, the phase values defining the CIR phase of each of the CIRs of the phase signals are located in the same time position in each of the CIR phases. In an embodiment, the CIR phase and the phase signal have phase values that vary according to time. In an embodiment, a phase extractor for forming a phase signal comprises: circuitry for forming a first candidate phase signal and a second candidate phase signal, wherein the first candidate phase signal is associated with phase values located only at a first time position in each of the CIR phases and the second candidate phase signal is associated with phase values located only at a second time position in each of the CIR phases; and circuitry for selecting the first candidate phase signal or the second candidate phase signal as the phase signal based on a respective amplitude or power associated with the first candidate phase signal or the second candidate phase signal exceeding a threshold level. In an embodiment, the target signal defines a time-varying phase value associated with a kick toward the vehicle, and wherein the object detector for detecting the moving object comprises circuitry for detecting the kick toward the vehicle. In an embodiment, the target signal defines time-varying phase values, which are associated with vital signs of a human being, and wherein the subject detector for detecting the moving subject comprises circuitry for detecting vital signs of a human being. In an embodiment, the target signal comprises a phase value that varies according to time, said phase value characterizing the moving object. In an embodiment, an object detector for detecting a moving object in a channel includes circuitry for determining that a correlation between a target signal and a phase signal exceeds a threshold level. In an embodiment, an object detector for detecting a moving object in a channel includes circuitry for providing a velocity of the moving object based on a phase signal. In an embodiment, the detector additionally includes a transmitter implemented with the circuitry to transmit the plurality of frames over the channel, wherein an Institute of Electrical and Electronics Engineers (IEEE)802.15.4 standard defines a format and content of the plurality of transmitted frames.

Some embodiments have been described above in detail, and various modifications are possible. The disclosed subject matter, including the functional operations described in this specification, can be implemented in electronic circuitry, computer hardware, firmware, software, or in combinations of them, such as the structural means disclosed in this specification and their structural equivalents: potentially including a program (e.g., program code encoded in a non-transitory computer-readable medium, which may be a memory device, storage device, machine-readable storage substrate, or other physical, machine-readable medium, or a combination of one or more of them) operable to cause one or more data processing devices, e.g., processors, to perform the operations described.

While this specification contains many specifics, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular implementations. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments.

The use of the phrase "at least one of" before a list with the conjunction "and" should not be taken as an exclusive list and should not be construed as a list of categories with one item from each category unless specifically stated otherwise. A sentence stating "A, B and at least one of C" may contain only one of the listed items, an integer multiple of the listed items, as well as one or more of the items in the list and another item not listed.

Other embodiments are within the scope of the following claims.

Claims

1. A method for detecting a moving object, the method comprising:

determining, by the detector, a CIR phase for each of the CIRs;

comparing, by the detector, the phase signal to a target signal; and

2. The method of claim 1, wherein the phase values defining the CIR phases of each of the CIRs of the phase signals are located in a same time position in each of the CIR phases.

3. The method of claim 1, wherein the CIR phase and the phase signal define a phase value that varies according to time.

4. The method of claim 1, wherein forming the phase signal comprises: forming a first candidate phase signal and a second candidate phase signal, wherein the first candidate phase signal is associated with phase values located only at a first time position in each of the CIR phases and the second candidate phase signal is associated with phase values located only at a second time position in each of the CIR phases; and selecting the first candidate phase signal or the second candidate phase signal as the phase signal based on a respective amplitude or power associated with the first candidate phase signal or the second candidate phase signal exceeding a threshold level.

5. The method of claim 1, wherein the target signal defines a phase value that varies as a function of time, the phase value indicating a kick toward a vehicle, and wherein detecting the moving object comprises detecting the kick toward the vehicle.

6. The method according to claim 1, wherein the target signal defines a phase value that varies according to time, the phase value being indicative of a vital sign of a human being, and wherein detecting the moving subject comprises detecting the vital sign of the human being.

7. The method of claim 1, wherein the target signal includes a time-varying phase value, the phase value characterizing the moving object.

8. The method of claim 1, wherein detecting the moving object in the channel comprises determining that a correlation between the target signal and the phase signal exceeds a threshold level.

9. The method of claim 1, wherein detecting the moving object in the channel comprises providing a velocity of the moving object based on an amplitude of the phase signal.

10. A moving object detector, comprising: